Ice Flow and Mass Changes of Lewis Glacier, Mount Kenya, East Africa: Observations 1974–86, Modelling, and Predictions to the Year 2000 AD

• Published in: Journal of Glaciology
• Main Author: Hastenrath, Stefan
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1989
• Subjects: Earth-Surface Processes; Journal of Glaciology; Lewis Glacier
• Online Access: http://dx.doi.org/10.1017/s0022143000009242; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000009242

Abstract The study is based on an observation program since 1974, including the continuous monitoring of net balance during 1978–86. The 8 year vertical net-balance profile, characterized by negative values throughout and an increase of absolute amounts from the higher towards the lower elevations, defines the recent climatic forcing. A model is developed with a spatial resolution by 100 m wide bands, relating glacier morphology, ice flow, and mass economy, using as input ice thickness, surface slope, width of height contours, area of 100 m wide bands, volume flux, and net balance as a function of elevation. In 1 year time steps, the model calculates the changes in ice thickness and surface topography commensurate with the difference between net balance and longitudinal divergence of volume flux, and then the corresponding changes in surface slope, contour width, area of 100 m wide bands, volume flux, and net balance corresponding to the new surface elevations. This information serves as input for the next time step. The model was applied to the intervals 1974–78, 1978–82, and 1982–86, as training periods, to explore the diagnostics of ice flow and mass economy, and to ascertain the model performance in treating long-term evolution in glacier behavior. The experiments yielded a reasonable agreement between calculated and observed changes in ice thickness, velocity, and volume flux, over the three aforementioned 4 year periods of field monitoring. Two sets of prediction experiments beyond 1986 were then undertaken. The first used as input the observed 1978–86 vertical net-balance profile (a), and thus simulated the future evolution of the glacier given continuation of the recent climatic forcing. In the second set of experiments, the 1978–86 net-balance values were doubled to yield a more extreme net-balance profile (b), representing climatic conditions considerably more adverse to the maintenance of the glacier. Predictions are presented for the epochs 1990, 1994, 1998, and 2000. Given continuation of the recent ...